Tunneling machine

ABSTRACT

A tunneling machine having a main support frame and also a movable frame which is longitudinally movable in stepwise fashion as the tunnel is being drilled, in which a main bearing assembly is utilized for transmitting both forward thrust and rotating drive to a cutting wheel, the main bearing assembly having a stator (housing) to which forward thrust is imparted by separate forward thrust drive means, the stator being attached to the forward end of the movable frame for pulling it forward, the main bearing assembly also including a rotor which directly drives the cutting wheel and which receives rotational drive through a mated pair of driving gears from the drive shaft of the machine; the rotor being supported from the stator by both radial and thrust bearings, and the pair of driving gears being longitudinally slidable so that vibration stresses from the cutting head are not transmitted back through the drive shaft to the rotating drive mechanism of the machine.

United States Patent [151 3,640,573 Safar Feb. 8, 1972 [54] TUNNELINGMACHINE Primary Examiner-Ernest R. Purser [72] Inventor: Frank Safar,Fullerton, Calif. Atmmey Beehlen Amt & Jagger [73] Assignee: Smithlntemational, lnc., Newport Beach,

Calif. [57] ABSTRACT [22] Filed; Ga 6, 1969 A tunneling machine having amain support frame and also a movable frame which is longitudinallymovable in stepwise [21] Appl' 863783 fashion as the tunnel is beingdrilled, in which a main bearing assembly is utilized for transmittingboth forward thrust and 52] us. CL ..299/31, 299/60, 299/90, matingdrive to a cutting wheel the main bearing assembly 1 308/174 having astator (housing) to which forward thrust is imparted [51 Int. Cl ..E01g3/04 by Fame fmwmd drive means the being [58] Field of Search "299/31 60308/174. 64/9 tached to the forward end of the movable frame for pullingit 64723 forward, the main bearing assembly also including a rotor whichdirectly drives the cutting wheel and which receives 56 R f rotationaldrive through a mated pair of driving gears from the l 1 e erences driveshaft of the machine; the rotor being supported from the UNITED STATESPATENTS stator by both radial and thrust bearings, and the pair ofdriving gears being longitudinally slidable so that vibration stresses1,647,853 11/1927 Budd et al ..308/ 174 X from the cutting head are nottransmitted back h h h 3,357,208 12/1967 Chase drive shaft to therotating drive mechanism of the machine. 3,383,138 5/1968 Scaravilli eta1 3,51 1,539 5/1970 Schonfeld ..299/3l X 17 Claims, 12 Drawing figuresI I l W 22 60 a TELESCO /NG 500 weusr 456's 65 an {N052 GEde 50X Z/0Haas/N6 80 M4l/V SOP/ 027' 2/5 FEAME\ MOTOQ fl/ysr mameae 6540016 FQAMEeAQ/AL //0 sis-Mew; fl 33 2 ,45; 54 /0//vc- 6542s /'"i:Q:1

-- A 5555/66 wee 250 E s .s a

2614.2 Side/N6 7'6Z$'C0 //V A03 466-5 H F007 PATENTED FEB 8 I972 SHEET 20F 9 PATENTEDFEB 8 I972 SHEET 3 OF 9 INVENTORY [FAA/Z 54/ /42 PATENTEUFEB 8 I972 SHEET 6 [IF 9 e mm M w PAIENIEDFEB am 3.40.57

SHEET 7 UF 9 INVENTOR. en/we 54/642 BY 61% /M PAIENIEBFEB 81972 sum 8 0r9 QQN PATENTEUFEB 8 I972 sum 9 0r 9 INVENTOR. 1 24466 541C142 TUNNELINGMACHINE BACKGROUND OF THE INVENTION The present invention relates totunneling machines having a rotary boring head or cutting wheel forcutting passages through hard rock and minerals. Machines of this typefrequently carry stress loads of a million pounds or more. The highdegree of hardness of material being cut reflects a heavy stress load onthe boring head or cutting wheel, and this stress load in turn must becarried by a bearing mechanism which permits the boring head or cuttingwheel to rotate, and must also be transmitted to other supportingportions of the machine.

It is well known in the art in a machine of this type to utilize a mainsupport frame and a movable frame, which are longitudinally movablerelative to each other, thus permitting a stepwise advance of themachine in a forwardly direction as the tunnel is being cut. The mainframe typically has a set of forward shoes and a set of rearward shoes,each of which may be extended for supportive engagement with the tunnelwall. The movable frame also has a forward shoe and a rearward shoewhich support both frames during the time when the main support frame isbeing relocated in the tunnel. A machine of this general type is shown,for example, in US. Pat. No. 3,383,138.

Heretofore, the machines of this general type have suffered from a veryshort useful life before rebuilding or major repair has been required.The primary object and purpose of the present invention is to provide animproved machine of the type described, which has a long useful lifebefore rebuilding or repairs are required.

An additional object of the invention is to provide a machine of theforegoing type, which is so arranged that a main bearing assemblysupporting the boring head or cutting wheel may be easily removed andreplaced without a substantial loss of the working time of the machine.

A further object of the invention is to provide a tunneling machine ofthe wheel type in which heavy cutting loads on the cutting wheel are notreflected into the rotating drive mechanism.

DRAWING SUMMARY FIG. I is a schematic diagram showing the main operativeparts of the machine;

FIG. 2 is a side elevational view of a tunneling machine in accordancewith the present invention, located in a cutting position within atunnel;

FIG. 3 is a vertical cross-sectional view of the machine taken on theline 33 of FIG. 2;

FIG. 4 is a vertical cross-sectional view of the machine taken on theline 4-4 of FIG. 2;

FIG. 5 is a vertical cross-sectional view of the machine taken on theline 55 of FIG. 2;

, FIG. 6 is a transverse cross-sectional view of the machine taken onthe line 6-6 of FIG. 3, but showing the rear end portion of the machine;

FIG. 7 is a longitudinal cross-sectional view of the front end portionof the machine taken on the line 7-7 of FIG. 3;

FIG. 8 is an enlarged view like FIG. 7;

FIG. 9 is a transverse cross-sectional view taken on the line 9-9 ofFIG. 8;

FIG. 10 is an interior detail view taken in the circle 10-10 of FIG. 8;

FIG. 1 l is an interior detail view taken in the circle llll of FIG. 8;

FIG. 12 is a perspective view of the easily removable main bearing ofthe machine.

PREFERRED EMBODIMENT GENERAL DESCRIPTION-FIG. l The tunneling machine ofthe present invention will first be generally described with referenceto FIG. I of the drawings.

LII

The tunneling machine includes a main support frame 50 having fronttelescoping legs 60 and rear telescoping legs 65 which are adapted foroutward extension to grip the tunnel wall. Thrust cylinders carried atthe forward end of main support frame 50 provide a forward thrust drivemeans and are expanded for driving the operative portions of the machinein a forwardly direction so as to force the cutting wheel 300 againstthe end face of the tunnel.

A movable frame is disposed within the main support frame 50, and islongitudinally movable relative to the main support frame. All of theoperative portions of the tunneling machine are connected or coupled,either directly or indirectly, to the movable frame 110. Thus themachineas a whole can be advanced stepwise in the forwardly direction. Theprocedure is that themain support frame 50 is located in a particularlongitudinal position within the tunnel; the telescoping legs 60 and 65are extended into engagement with the tunnel walls so as to rigidlysupport the main support frame in that location; and the thrustcylinders 80 are then expanded forwardly until a particular cuttingstroke has been completed. Auxiliary shoes 160 and 165, associated withthe forward and rearward ends, respectively, of the movable frame 110are then used for supporting the entire machine while the main supportframe 50 is being relocated to a more forwardly advanced position. Thisgeneral mode of advancing the machine is well known in the art and henceneed not be described in further detail.

Although the specific mechanism is not shown in FIG. I, the movableframe 110 is supported in a nonrotative relationship to the main supportframe 50, but is free to move longitudinally relative to the mainsupport frame 50, and is preferably supported in a longitudinal slidingrelationship relative to the main frame 50.

A main drive shaft is disposed inside the movable frame 110, and isadvanced along the tunnel in conjunction with the movement of themovable frame. A rear bearing I25 supports the rearward end of driveshaft 130 for rotation relative to movable frame 110. A gear box isattached to the rear- -ward end of movable frame 110, and is alsocoupled to the rearward end of the main drive shaft 130. A drive motorassociated with gear box 135 is operable for imparting a rotating driveto the drive shaft 130, so that the drive shaft will rotate relative tothe movable frame 110. The rear auxiliary shoe I65, although it could beattached directly to the rearward end of movable frame 110, is forconvenience attached underneath the gear box 135.

To complete the rotating drive mechanism a pair of driving gears 150,are located at the forward end of the main drive shaft 130. The drivegear ISO is a male gear which is rigidly attached to the forward end ofdrive shaft 130. The driving gear 155 is a female gear which is rigidly(but removably) attached to the rotor 220 of main bearing assembly 200.An important feature of the present invention is that the female gear155 is free to slide longitudinally, at least to some extent, relativeto the male drive gear 150. The significance of that feature of themachine will be described subsequently.

A main bearing assembly 200 is used to support and to drive the maincutting wheel 300, and concurrently receives both the forward thrustdrive from thrust cylinders 80 and the rotating drive from drive shaft130. The main bearing assembly 200 includes a housing or stator 210which is of a generally hollow cylindrical configuration. A rotor 220 isdisposed concentrically within the housing 210, and is supported forrotation relative to the housing by means of a front end radial bearing240 and a rear end radial bearing 250. Removable attachment means suchas bolts 221 are employed for removably attaching the female drive gearI55 to the rearward end of rotor 220. Removable attachment means such asbolts 222 are used for removably attaching the main cutting wheel 300 tothe forward end of rotor 220.

The rearward end of housing or stator 210 is removably at-. tached tothe forward end of movable frame 110, as by means of bolts 211. Theforward thrust of the thrust cylinders 80 is applied to a thrust collar215 fonned on the housing 210, hence the forward thrust of the thrustcylinders 80 serves to pull the movable frame 1 in a forwardlydirection.

Also located between the housing 210 and the rotor 220 is a thrustbearing 230, which is disposed intermediate to the forward and rearwardend bearings. The function of the thrust bearing 230 is to impart aforward thrust drive from the housing' or stator 210 into the rotor 220.The associated mechanism includes an interior thrust collar 217 on thehousing 210 which has a forwardly facing thrust shoulder, and anexterior thrust collar 225 on the rotor 220 which has a rearwardlyfacing thrust shoulder, the thrust bearing 230 being supported betweenthese two thrust shoulders.

The forward auxiliary shoe 160, although it could be attached directlyto the forward end of movable frame 110, is for convenience attachedunder the housing 210.

During a cutting operationof the machine the cutting wheel 300 receivesboth rotational and thrust loadings which vary over a wide range in arather unpredictable manner, with the peak loadings being very high. Inmost or all of the prior art machines for tunneling in hard rock or hardminerals, the longitudinal thrust force of the machine as well asvibrational stresses are imparted through the main drive shaft into therotating drive mechanism. According to the present invention, however,the female drive gear 155 is longitudinally slidable relative to themale drive gear 150, hence the longitudinal and vibrational stressesimparted from cutting wheel 300 to rotor 220 are not transmitted to thedrive shaft 130, except perhaps with a greatly reduced magnitude. Thegear box 135 is thus protected from any extraneous interference, and isfree to perform its simple function of imparting a rotating drive to thedrive shaft 130, under conditions which permit it to have a long usefullife and to operate relatively free of maintenance requirements.

Another significant feature of the invention is that the main bearingassembly 200 is arranged for easy removal, in its-entirety, from thetunneling machine. Thus the coupling of thrust cylinders 80 to thethrust collar 215 of housing 210 is such as to permit easy detachment ofthe housing 210 from the'thrust cylinders. Removable bolts 211 alsopermit easy detachment of housing 210 from the movable frame 1 10.Removable bolts 221 permit easy detachment of female drive gear 155 fromrotor 220, and removable bolts 222 permit easy detachment of cuttingwheel 300 from the rotor. The radial bearings 240 and 250, and thethrust bearing 230, involve a large number of individual parts, andthese bearing mechanisms tend to wear during operation of the machine.The easily removable nature of the attachments of housing or stator 210and of rotor 220 to the other parts of the machine makes it possible toremove the entire main bearing assembly 200 as a unit. A new mainbearing assembly may be inserted in the tunneling machine withcomparatively small loss of working time. The worn or damaged mainbearing assembly may then be transported away from the construction jobto a shop or factory where its repair or overhaul may be conducted on amore leisurely ba- SIS.

In utilizing the tunneling machine of the present invention it may bepreferred, however, to replace the main bearing assembly 200periodically as a preventive maintenance feature. In that case, the mainbearing assembly which is removed may not be significantly worn ordamaged at all, but replacing the old assembly with a new one involvesonly a short down time for the machine and insures a long uninterruptedoperating time for the machine when its useage is resumed.

DETAILED DESCRIPTIONFIGS. 2 to 12 The presently preferred embodiment ofthe invention, as illustrated in drawing FIGS. 2 to 12, inclusive, willnow be described in some detail.

The structure and operation of the machine has already been describedwith reference to FIG. 1, where the various component parts of themachine are illustrated schematically, rather than in accordance withtheir precise mechanical construction. The reference numbers used inFIG. 1 are also applied to the corresponding parts of the machine inFIGS. 2 through 12, hence it will be understood that in FIG. 1 theparticular reference number applies to a schematic representation of thepart, whereas in FIGS. 2 through 12 the same reference number indicatesthe actually preferred, precise form of the same part.

The schematic representation of the machine in FIG. 1 ignores the factthat in addition to the circular main cutting wheel 300 the machine alsoincludes a center drill 400. The detailed drawings illustrate a drivemechanism and a bearing support assembly for the center drill, which areconcentrically arranged relative to the main drive shaft and mainbearing assembly. Before going into a detailed description of the'centerdrill and its associated bearing assembly and drive mechanism, however,it will be advantageous to describe in detail the main portions of themachine which have already been discussed in connection with FIG. 1.

Thus the main support frame 50 has a square cross-sectionalconfiguration and is formed of two separate frame halves 52, 54 whichare joined together by bolts 58 (FIG. 4). Each of the telescoping frontlegs 60 has a leg base 62 onto which ribs 56 are attached for purposesof structural reinforcement. Similar rib structures are also associatedwith the leg bases 67 of the rear telescoping legs 65. Wear bars 70 areattached to the interior corners of the housing structure 52-54 andprovide surfaces within which the guide tube 115 may slidelongitudinally. The wear bars 70 are preferably made of machined brassmaterial.

The actual physical structure of movable frame 110 includes a guide tube115 whose cross-sectional configuration is in the form of a hollowsquare (FIG. 4) and which extends throughout the greater part of thelength of the machine. The exterior corner surfaces of guide tube 115slide within the wear bars 70, the wear bars being located at both theforward and the rearward ends of housing 50. A circular ring 117 iswelded onto the forward end of guide tube 115 (FIG. 7 and 8) and formsthe forward end portion of movable frame 110. A v

circular ring 119 is welded to the rearward end of guide tube 115 andforms the rearward end portion of movable frame 1 10.

A front bellows and a rear bellows 77 constitute, in a sense, extensionsof the main support frame 50 (FIG. 2). The purpose of these bellows isto prevent dirt and other foreign materials from entering into theinterior spaces between housing 50 and guide tube 1 15, in which aprecisely controlled Ion gitudinal sliding action of the movable frame110 needs to be achieved. The front bellows 75 therefore has itsrearward end attached to the front end of housing 50 and its forward endattached to the guide tube forward ring 117 (FIG. 8). The rear bellows77 has its forward end attached to the rearward end of housing 50 whileits rearward end is attached to the ring 119 (FIG. 6).

There are four of the thrust cylinders 80 located at the top, bottom,and sides of main support frame 50 (FIG. 3). Each thrust cylinder has anassociated cylinder rod 83 which is extendable in the forward directionfor imparting the thrust force. A removable thrust collar 85 slides overthe rearward portion of housing 210 of the main bearing assembly (FIGS.2, 7) and has circumferentially spaced ears 86 in which pins 87 arecarried, each pin 87 being pivotally connected to the forward end of theassociated rod 83. Removable bolts 88 are used to attach the forward endof thrust collar 85 to the thrust collar 215 of housing 210. Thespecific configuration of thrust collar 215 is shown in FIGS. 7, 8, and12.

The main drive motor 140 which is schematically illustrated in FIG. 1 bya single block is in fact a group of six separate motors disposed aboutthe periphery of gear box 135 (FIGS. 2,5). Each of these motors drives abull gear 137 (not shown) which 'is attached to the rearward end ofdrive shaft 130. During cutting operations of the machine the forwardend of drive shaft is supported by the gears 150, 155. When the mainbearing assembly 200 is removed from the machine, however,

it becomes necessary to independently support the front end of the driveshaft, and for this purpose a support ring 127 is provided within theforward end of guide tube 115.

In the main bearing assembly the front radial bearing 240 has an innerring or raceway 242, an outer ring or raceway 246, and cylindricalbearings 244 which are retained between the two raceways. A frontbearing retainer 260 is attached both to the housing 210 and to therotor 220 for shielding the bearing 240 from dirt.

Rear radial bearing 250 includes an inner ring or raceway 252, an outerring or raceway 256, and cylindrical bearings 254 which are disposedbetween and retained by the two raceways. There are two separateretainers for the rear bearing, the outer one being designated as 270and the inner one as 280 (FIG. 8). A rotary seal 275 is located betweenretainers 270,280.

Thrust bearing 230 includes a rear thrust plate or ring 231 which issupported from the thrust collar 217 of housing 210. A bearing cage 233(FIGS. 8, 9 and 10) has radial legs, and on each radial leg there arethree cylindrical bearing members 234 disposed for rotation. The thrustring or plate 231 lies in a plane that is transverse to the longitudinalaxis of rotor 220, and the outer circumferential surface of ring 231firmly engages the interior wall surface of housing 210 while its innercircumferential surface is spaced away from the rotor 220. Thecylindrical bearing members 234 ride on the forward flat surface of therear pressure plate 231, and also ride on the rear flat surface of therear pressure plate 231, and also ride on the rear flat surface of aforward pressure plate 235. Pressure plate 235 is disposed parallel tothe pressure plate 231, having its interior circumferential surface infirm engagement with the exterior surface of rotor 220 to rotatetherewith while its outer circumferential surface is spaced away fromhousing 210. The forward flat surface of pressure ring 235 bears againsta spacer ring 225.

It will be noted that in FIG. 1 the reference numeral 225 applies to apart which is schematically illustrated as a thrust collar formed on theexterior surface of rotor 220. In the preferred embodiment of theinvention, however, the member 225 is in fact a spacer ring which isslid over the exterior surface of rotor 220, the forward edge of thespacer ring being lodged against inner raceway 242 of the front radialbearing 240. The raceway 242 is, in turn, lodged against a shoulder 226of rotor 220. Hence, the spacer ring 225 is supported against forwardmotion relative to the rotor 220, and forward thrust bearing 230 isoperative to impart forward thrust from housing 210 into the rotor 220in the manner which is schematically illustrated in FIG. 1.

The tunneling machine of the present invention is designed for a forwardloading on the cutting wheel of approximately 1 million pounds, and thisforward loading is also carried by the thrust bearing 230, thusinvolving the possibility of a substantial deformation of the componentparts of the thrust bearing and associated mechanism. Before placing themachine in operation the parts are aligned in such a way that a rearthrust plate 231 of thrust bearing 230 is spaced a predetermined amount,such as 0.030 inches, from the thrust collar 217 of housing 210. Aplurality of recesses 218 are formed in the thrust collar 217, and aseparate compression spring 232 is placed within each of the recesses218 so as to provide a forward pressure against the thrust plate 231,Associated peepholes 212 are formed in the housing 210 so that theinitial spacing between thrust plate 231 and thrust collar 217 can beobserved, measured, and hence established at its proper value.

The main cutting wheel 300 includes a central hub portion 310 which ismachined so as to fit precisely over the forward end of rotor 220. Theouter or main part of the cutting wheel and the hub portion are weldedtogether to form an integral structure. A number of the bolts 222 passthrough corresponding openings in hub portion 310 and into appropriatelylocated threaded openings of the rotor 220. (FIG. 7). Cutters 320 aremounted about the circumference and face of the cutting wheel 300, asshown in FIG. 2. In the preferred embodiment of the invention there maytypically be 31 of these cutters.

The thrust cylinders which are used to drive the machine forward duringits cutting stroke may also be used for retracting the cutting wheel 300away from the tunnel face. The bolts 88 (FIG. 7) provide a positivecoupling to the main bearing housing 210 so that it may be withdrawn inthe rearward direction. Thrust bearing 230 is effective for thrustingthe rotor 220 forward but is not effective in retracting the rotor.However, rear bearing 250 in conjunction with the inner bearing retainer280 is effective to impart a withdrawing motion from the housing 210 tothe rotor 220. The rearward motion of housing 210 is imparted throughradial bearing 250 to the outer circumferential portion of bearingretainer 280. The inner circumferential portion of bearing retainer 280is fastened to rotor 220 by means of bolts 281 (FIG. 1) and is thereforeeffective to withdraw the rotor 220. Thus a withdrawing action of thethrust cylinders 80 is effective to withdraw cutting wheel 300 from thetunnel face.

The main drive shaft is hollow (FIGS. 4, 5, 8) thus permitting a centerdrill drive shaft 410 to pass through its entire length. A separatedrive motor 420 mounted on gearbox (FIG. 2) drives the center drilldrive shaft 410 relative to the movable frame 110. A center drillbearing assembly 450 (FIG. 8), which is generally similar to the mainbearing assembly 200, supports the center drill 400 to be driven by thecenter drill drive shaft 410.

More specifically, the center drill bearing assembly 450 includes arotor 460 having on its rearward end the male portion 461 of a splinedcoupling. The female portion 411 is attached to the forward end of driveshaft 410. The splined coupling permits a longitudinal slidingrelationship between drive shaft 410 and rotor 460. The forward end ofrotor 460 projects beyond the hub 310 of the main cutting wheel andprovides a hub or base for attachment of the center drill 400.

Center drill bearing assembly 450 also includes a housing 470 that isreceived within a forward recess 227 formed in the rotor 220, androtates with the rotor 220. Lugs 471 (FIG. 3) attached to the forwardend of housing 470 are received in small circumferentially spacedrecesses in the hub 310. Bolts 472 which pass through the lugs 471permit housing 470 to slide longitudinally relative to rotor 220. Thusthe housing 470 of the center drill bearing assembly rotates with rotor220 of the main bearing assembly, while the rotor 460 is directly drivenby shaft 410.

Rotor 460 is supported for rotation relative to housing 470 by a frontradial bearing 480 and a rear radial bearing 490, and while thestructure of these radial bearings is not identical to the structure ofradial bearings 240 and 250 their operation is nevertheless very muchthe same. A front bearing retainer 482 is attached around hub 462 andextends to the forward end of housing 470 so as to protect radialbearing 480 from dirt. A thrust bearing 485 is located intermediate tothe radial bearings 480 and 490, and its structure and function are verymuch like that of the thrust bearing 230 which was previously described.That is, forward thrust received from the housing 470 is impartedthrough thrust bearing 485 into rotor 460 and hence into the centerdrill 400.

In accordance with the preferred usage of the machine the main cuttingwheel 300 is driven at a relatively slow rate, such as 10 revolutionsper minute, while the center drill 400 is driven at a more rapid rate,such as 30 revolutions per minute. By reversing motor 420 the centerdrill 400 may, if desired, be rotated opposite to the main cuttingwheel.

The center drill bearing assembly 450 also includes a preloadingmechanism which has no counterpart in the main bearing assembly 200. Therotor 220 has a cylindrical recess 227 formed in its forward end (FIG.8), and the depth of the recess 227 is considerably greater than what isnecessary to accommodate the housing 470 of the center drill bearingansemhly. The prcloading assembly generally designated as 500 includes aforward plate 501 which is of generally circular configuration, buthaving a central opening through which the female coupling 411 extends.The preloading assembly 500 also includes a generally circular rearplate 502. A plurality of bolts 503 are spaced about the circumferencesof the two plates 501, 502 and are utilized to retain these plates inproximity to each other. The plate 502 has a central opening whichsurrounds the drive shaft 410, but not in direct engagement with it, sothat drive shaft 410 is permitted to rotate relative to the plate 502.To the rear of recess 227 the rotor 220 is further recessed, withsmaller diameter opening, in order to permit the pilot drill drive shaft410 to be received therein. Thus the recess 227 forms a circumferentialshoulder which faces in a forwardly direction within the rotor 220. Theouter circumfer ential edge of plate 502 bears against thiscircumferential shoulder and thus provides the basis for supportingcenter drill 40 for forward thrust. The inner circumferential portion ofplate 502 is recessed on its front side so as to receive a set ofBelleville disc springs 504. The springs 504 push the plate 501 forwardrelative to the plate 502, but the total displacement is limited by thebolts 503. The forward surface of plate 501 bears tight against therearward end of housing 470 (except for a bearing retainertherebetween).

The entire housing 470 of the center drill bearing assembly 450 is freeto slide longitudinally, to some extent, relative to the rotor 220 andhub 310. Lugs 471 are welded to the housing 470 and hence move with thehousing. Bolts 472 are firmly retained in threaded openings in the rotor220 and in the hub 310, but the openings through which they pass in thelugs 471 are not threaded, hence the lugs 471 may slide rearwardly alimited distance relative to the bolts 472.

The purpose of the preloading assembly 500 is to permit the center drill400 to retract under excessive load. For example, when the machine isbuilt with a cutting wheel diameter of 13 feet and is designed for atotal thrust of 1 million pounds against the tunnel face, for cuttingmaterial which has a compressive strength of 30,000 pounds per squareinch, the design load for the center drill 400 is then 90,000 pounds offorward thrust. The preload assembly 500 is then set to this load valueof 90,000 pounds, and in the event the center drill receives a load inexcess of that amount it will move rearwardly a small distance relativeto the main cutting wheel 300, thus minimizing the shock on the centerdrill and protecting it against damage.

The preloading is accomplished by placing the springs 504 under acompressive stress of 90,000 pounds and then tightening the bolts 503 sothat the plates 501, 502 will retain the springs in their compressedcondition. A gap 505 between plates 501, 502 would permit furthercompression of the springs 504. However, under normal operatingconditions the thrust load on the center drill is 90,000 pounds or less,hence the springs 504 are not required to accept any additionalcompression and the gap 505 does not close even partially. But if anoverload for the center drill is encountered then that overload will bepicked up by the springs 504, and the center drill together with itsbearing assembly 450 will be permitted to retract relative to the maincutting wheel. Lugs 471 will move rearwardly relative to hub 310 and thegap 505 will commence to close.

For purpose of moving the machine into and out of a tunnel, andtransporting it, it is necessary to disassemble the main cutting wheel300. With reference to HO. 4, there is illustrated a removable spoke 330of the main cutting wheel, which can be detached from the centralportion of the cutting wheel simply by removing a number of bolts. Thisillustrated detail is typical of the cutting wheel construction andindicates the manner in which the entire cutting wheel may bedisassembled for convenience in transportation.

It is possible to remove and replace both the main bearing assembly 200and the center drill bearing assembly 450 in a very limited time, suchas two or three hours where an overload crane and other shop equipmentare available, or perhaps 2 or 3 days under conditions which prevailinside a tunnel. The procedure for removing and replacing these twobearings will now be briefly described.

First the entire machine is retracted from the tunnel face, a distanceof about l0 feet. Then the center drill 400 and its bearing assembly 450are removed. This is accomplished simply by removing the nuts from thebolts 472, and the entire housing 470 together with the associatedpreload assembly 500 slides out of recess 227 of the rotor 220. Thesplined coupling 461 41 1 simply separates.

The next step is to remove the main cutting wheel 300. This is done byremoving bolts 222 (FIG. 7). The hub 310 then simply slips off theforward end of rotor 220. The next step is to expand the thrustcylinders so as to move the movable frame about two feed forward fromits most rearwardly position. Access can then be obtained to the bolts211, of which in the presently preferred form of the machine there are48 spaced about the periphery of the front guide tube ring Thereafter,the bolts 88 are removed and the thrust cylinders 80 are retracted so asto draw the thrust collar 85 rearwardly. It is then possible to pull themain bearing assembly 200 in a forwardly direction and remove it fromcontact both with the guide tube flange 117 and with the thrust collar85. The female gear may then be detached from rotor 220 by removing thebolts 221.

As a convenience in performing these operations it is desirable toprovide a small rearward extension (not shown in the present drawings)on thrust collar 85. This extension serves to support the thrust collar85 from the guide tube ring 117 both during and after the time when thebolts 211 are removed. Another desirable convenience is a platform whichcan be positioned in front of the machine to receive the main bearingassembly 200 when it is removed.

The female drive gear 155 may be attached to the replacement mainbearing unit, which can then be inserted into the machine by followingthe reverse of the procedure described above. After the main bearingassembly has been replaced a new pilot drill bearing assembly isinserted, again by following the reverse of the described procedure.

What is claimed as new is:

l. A tunneling machine comprising:

a main support frame having front and rear sets of telescoping legsadapted for outward extension to grip the tunnel wall;

a movable frame which is supported within the main support frame innonrotative but longitudinally movable relationship thereto;

a generally circular cutting wheel at the forward end of the machine;

a drive shaft carried within the movable frame and rotatable relativethereto for imparting rotating drive to the cutting wheel;

rotating drive means carried on the movable frame for drivingly rotatingthe drive shaft;

a main bearing assembly including a stator having a generally hollowcylindrical configuration, a rotor disposed within said stator, andbearing means supporting said rotor for rotation relative to saidstator;

said drive shaft terminating rearwardly of said main bearing assemblyand said rotor having its rearward end removably coupled to said driveshaft and its forward end removably coupled to said cutting wheel, saidstator having its rearward end coupled to the forward end of saidmovable frame;

and forward thrust drive means carried on the main support frame anddrivingly coupled to said stator for advancing the cutting wheel,movable frame, and drive shaft whereby the rotating drive from saidrotating drive means is concurrently imparted through said drive shaftand said rotor to said cutting wheel.

2. A tunneling machine as claimed in claim 1 which includes auxiliaryshoes cooperatively associated with the front and rear ends of saidmovable frame for supporting both frames when the main support frame isbeing advanced to a new position within the tunnel, and wherein thefront auxiliary shoe is attached to said stator of said main bearingassembly.

3. A tunneling machine as claimed in claim 1 which includes removablebolts attaching said rotor to said cutting wheel, attaching said rotorto a drive gear coupled to said drive shaft, and attaching said statorto said movable frame.

4. A tunneling machine as claimed in claim 1 which includes a femaledrive gear removably attached to the rearward end of said rotor by meansof bolts, and a male drive gear attached to said drive shaft, said drivegears being relatively slidable longitudinally of said drive shaft.

5. A tunneling machine as claimed in claim 1 which includes a matingpair of driving gears which drivingly couple said rotor to said driveshaft, one of said driving gears being attached to said drive shaft andthe other of said driving gears being attached to said rotor, said gearsbeing slidable relative to each other along the longitudinal axis of thedrive shaft whereby longitudinal vibrations imparted from the cuttingwheel to the rotor are not transmitted to said rotating drive means.

6. A tunneling machine as claimed in claim 1 wherein the couplings ofsaid rotor to said drive shaft and to said cutting wheel are arrangedfor easy detachment, and wherein the couplings of said stator to saidmovable frame and to said forward thrust drive means are also arrangedfor easy detachment, whereby said main bearing assembly may be easilyremoved and replaced in its entirety.

7. A tunneling machine as claimed in claim 6 which includes a matingpair of driving gears which drivingly couple said rotor to said driveshaft, one of said driving gears being attached to said drive shaft andthe other of said driving gears being attached to said rotor, said gearsbeing slidable relative to each other along the longitudinal axis of thedrive shaft whereby longitudinal vibrations imparted from the cuttingwheel to the rotor are not transmitted to said rotating drive means.

8. A tunneling machine as claimed in claim 1 wherein said bearing meansincludes separate radial bearings disposed between said stator and rotorat their forward and rearward ends, respectively, and a thrust bearingdisposed between said stator and rotor intermediate their ends, saidthrust bearings being retained between an interior thrust collar of saidstator having a forwardly facing thrust shoulder and an exterior thrustcollar of said rotor having a rearwardly facing thrust shoulder.

9. A tunneling machine as claimed in claim 8 wherein said radialbearings include cylindrical bearing members, and said thrust bearingalso includes cylindrical bearing members disposed perpendicular to thebearing members of said radial bearings.

10. A tunneling machine as claimed in claim 8 wherein the couplings ofsaid rotor to said drive shaft and to said cutting wheel are arrangedfor easy detachment, and wherein the couplings of said stator to saidmovable frame and to said forward thrust drive means are also arrangedfor easy detachment, whereby said main bearing assembly may be easilyremoved and replaced in its entirety.

11. A tunneling machine as claimed in claim 10 which includes a matingpair of driving gears which drivingly couple said rotor to said driveshaft, one of said driving gears being attached to said drive shaft andthe other of said driving gears being attached to said rotor, said gearsbeing slidable relative to each other along the longitudinal axis of thedrive shaft whereby longitudinal vibrations imparted from the cuttingwheel to the rotor are not transmitted to said rotating drive means.

12. A tunnel machine as claimed in claim 8 which includes a mating pairof driving gears which drivingly couple said rotor to said driver shaft,one of said driving gears being attached to said drive shaft and theother of said driving gears being attached to said rotor, said gearsbeing slidable relative to each other along the longitudinal axis of thedrive shaft whereby longitudinal vibrations imparted from the cuttingwheel to the rotor are not transmitted to said rotating drive means.

13. A tunneling machine comprising: a main support frame having frontand rear sets of telescoping legs adapted for outward extension to gripthe tunnel walls a movable frame supported within the main support framein non-rotative but longitudinally movable relationship thereto;

a drive shaft supported by the movable frame in rotatable relationshipthereto;

rotating drive means carried on the movable frame for drivingly rotatingthe drive shaft,

a main bearing assembly including a stator having a generally hollowcylindrical configuration, a rotor disposed within said stator, radialbearing means supporting said rotor for.rotation relative to saidstator, and thrust bearing means for driving said rotor forward whensaid stator moves forward;

said stator having its rearward end removably coupled to the forward endof said movable frame;

said drive shaft terminating rearwardly of said main bearing assembly,and said rotor having its rearward end removably coupled to said driveshaft;

a generally circular cutting wheel at the forward end of the machine,removably coupled to the forward end of said rotor;

and forward thrust drive means carried on the main support frame anddrivingly coupled to said stator for advancing the bearing assembly,drive shaft, movable frame, and cutting wheel while a rotating drive isconcurrently imparted from said rotating drive means through said driveshaft and said rotor to said cutting wheel;

the attachment of said stator to said forward thrust drive means beingalso removable whereby said main bearing assembly may be detached as acomplete unit from the remainder of the tunneling machine.

14. A tunneling machine as claimed in claim 13 which includes a matingpair of driving gears which drivingly couple said rotor to said driveshaft, one of said driving gears being attached to said drive shaft andthe other of said driving gears being attached to said rotor, said gearsbeing slidable relative to each other along the longitudinal axis of thedrive shaft whereby longitudinal vibrations imparted from the cuttingwheel to the rotor are not transmitted to said rotating drive means.

15. A tunneling machine as claimed in claim 13 which includes aplurality of removable bolts coupling the rearward end of said rotor tosaid driving shaft and a plurality of removable bolts attaching saidstator to said movable frame.

16. A tunneling machine as claimed in claim 13 wherein said cuttingwheel and said rotor have a centrally located recess formed therein, andwhich further includes a center drill disposed at the center of saidcutting wheel and in front of said recess, and resilient support meansdisposed within said recess and attached to said center drill fordrivingly supporting the same.

17. A tunneling machine as claimed in claim 16 wherein said resilientsupport means includes spring means compressible in a directionperpendicular to the plane of said cutting wheel, and means confiningsaid spring means in a compressed condition at a predetermined initialforce level.

a: i i

1. A tunneling machine comprising: a main support frame having front andrear sets of telescoping legs adapted for outward extension to grip thetunnel wall; a movable frame which is supported within the main supportframe in nonrotative but longitudinally movable relationship thereto; agenerally circular cutting wheel at the forward end of the machine; adrive shaft carried within the movable frame and rotatable relativethereto for imparting rotating drive to the cutting wheel; rotatingdrive means carried on the movable frame for drivingly rotating thedrive shaft; a main bearing assembly including a stator having agenerally hollow cylindrical configuration, a rotor disposed within saidstator, and bearing means supporting said rotor for rotation relative tosaid stator; said drive shaft terminating rearwardly of said mainbearing assembly and said rotor having its rearward end removablycoupled to said drive shaft and its forward end removably coupled tosaid cutting wheel, said stator having its rearward end coupled to theforward end of said movable frame; and forward thrust drive meanscarried on the main support frame and drivingly coupled to said statorfor advancing the cutting wheel, movable frame, and drive shaft wherebythe rotating drive from said rotating drive means is concurrentlyimparted through said drive shaft and said rotor to said cutting wheel.2. A tunneling machine as claimed in claim 1 which includes auxiliaryshoes cooperatively associated with the front and rear ends of saidmovable frame for supporting both frames when the main support frame isbeing advanced to a new position within the tunnel, and wherein thefront auxiliary shoe is attached to said stator of said main bearingassembly.
 3. A tunneling machine as claimed in claim 1 which includesremovable bolts attaching said rotor to said cutting wheel, attachingsaid rotor to a drive gear coupled to said drive shaft, and attachingsaid stator to said movable frame.
 4. A tunneling machine as claimed inclaim 1 which includes a female drive gear removably attached to therearward end of said rotor by means of bolts, and a male drive gearattached to said drive shaft, said drive gears being relatively slidablelongitudinally of said drive shaft.
 5. A tunneling machine as claimed inclaim 1 which includes a mating pair of driving gears which drivinglycouple said rotor to said drive shaft, one of said driving gears beingattached to said drive shaft and the other of said driving gears beingattached to said rotor, said gears being slidable relative to each otheralong the longitudinal axis of the drive shaft whereby longitudinalvibrations imparted from the cutting wheel to the rotor are nottransmitted to said rotating drive means.
 6. A tunneling machine asclaimed in claim 1 wherein the couplings of said rotor to said driveshaft and to said cutting wheel are arranged for easy detachment, andwherein the couplings of said stator to said movable frame and to saidforward thrust drive means are also arranged for easy detachment,whereby said main bearing assembly may be easily removed and replaced inits entirety.
 7. A tunneling machine as claimed in claim 6 whichincludes a mating pair of driving gears which driVingly couple saidrotor to said drive shaft, one of said driving gears being attached tosaid drive shaft and the other of said driving gears being attached tosaid rotor, said gears being slidable relative to each other along thelongitudinal axis of the drive shaft whereby longitudinal vibrationsimparted from the cutting wheel to the rotor are not transmitted to saidrotating drive means.
 8. A tunneling machine as claimed in claim 1wherein said bearing means includes separate radial bearings disposedbetween said stator and rotor at their forward and rearward ends,respectively, and a thrust bearing disposed between said stator androtor intermediate their ends, said thrust bearing being retainedbetween an interior thrust collar of said stator having a forwardlyfacing thrust shoulder and an exterior thrust collar of said rotorhaving a rearwardly facing thrust shoulder.
 9. A tunneling machine asclaimed in claim 8 wherein said radial bearings include cylindricalbearing members, and said thrust bearing also includes cylindricalbearing members disposed perpendicular to the bearing members of saidradial bearings.
 10. A tunneling machine as claimed in claim 8 whereinthe couplings of said rotor to said drive shaft and to said cuttingwheel are arranged for easy detachment, and wherein the couplings ofsaid stator to said movable frame and to said forward thrust drive meansare also arranged for easy detachment, whereby said main bearingassembly may be easily removed and replaced in its entirety.
 11. Atunneling machine as claimed in claim 10 which includes a mating pair ofdriving gears which drivingly couple said rotor to said drive shaft, oneof said driving gears being attached to said drive shaft and the otherof said driving gears being attached to said rotor, said gears beingslidable relative to each other along the longitudinal axis of the driveshaft whereby longitudinal vibrations imparted from the cutting wheel tothe rotor are not transmitted to said rotating drive means.
 12. Atunneling machine as claimed in claim 8 which includes a mating pair ofdriving gears which drivingly couple said rotor to said drive shaft, oneof said driving gears being attached to said drive shaft and the otherof said driving gears being attached to said rotor, said gears beingslidable relative to each other along the longitudinal axis of the driveshaft whereby longitudinal vibrations imparted from the cutting wheel tothe rotor are not transmitted to said rotating drive means.
 13. Atunneling machine comprising: a main support frame having front and rearsets of telescoping legs adapted for outward extension to grip thetunnel walls; a movable frame supported within the main support frame innon-rotative but longitudinally movable relationship thereto; a driveshaft supported by the movable frame in rotatable relationship thereto;rotating drive means carried on the movable frame for drivingly rotatingthe drive shaft; a main bearing assembly including a stator having agenerally hollow cylindrical configuration, a rotor disposed within saidstator, radial bearing means supporting said rotor for rotation relativeto said stator, and thrust bearing means for driving said rotor forwardwhen said stator moves forward; said stator having its rearward endremovably coupled to the forward end of said movable frame; said driveshaft terminating rearwardly of said main bearing assembly, and saidrotor having its rearward end removably coupled to said drive shaft; agenerally circular cutting wheel at the forward end of the machine,removably coupled to the forward end of said rotor; and forward thrustdrive means carried on the main support frame and drivingly coupled tosaid stator for advancing the bearing assembly, drive shaft, movableframe, and cutting wheel while a rotating drive is concurrently impartedfrom said rotating drive means through said drive shaft and said rotorto said cutting wheel; the attachment of said stator to said forwardthrust drive means being also removable whereby said main bearingassembly may be detached as a complete unit from the remainder of thetunneling machine.
 14. A tunneling machine as claimed in claim 13 whichincludes a mating pair of driving gears which drivingly couple saidrotor to said drive shaft, one of said driving gears being attached tosaid drive shaft and the other of said driving gears being attached tosaid rotor, said gears being slidable relative to each other along thelongitudinal axis of the drive shaft whereby longitudinal vibrationsimparted from the cutting wheel to the rotor are not transmitted to saidrotating drive means.
 15. A tunneling machine as claimed in claim 13which includes a plurality of removable bolts coupling the rearward endof said rotor to said driving shaft and a plurality of removable boltsattaching said stator to said movable frame.
 16. A tunneling machine asclaimed in claim 13 wherein said cutting wheel and said rotor have acentrally located recess formed therein, and which further includes acenter drill disposed at the center of said cutting wheel and in frontof said recess, and resilient support means disposed within said recessand attached to said center drill for drivingly supporting the same. 17.A tunneling machine as claimed in claim 16 wherein said resilientsupport means includes spring means compressible in a directionperpendicular to the plane of said cutting wheel, and means confiningsaid spring means in a compressed condition at a predetermined initialforce level.